Build Your Own Clone Message Board

The new (Nov. '17) Classic Phaser kit can be built to either "script logo" or "block logo" specs, referring to different versions of the MXR Phase 90, upon which this kit is based. The difference between the two is just a single resistor in a feedback loop that introduces a bit of signal regeneration in the latter version. While the Script version is the better known/more popular of the two, the Block has its devotees, as well.

But there's no need to choose one over the other when you build the Classic Phaser, since you can have both versions available with the flip of a switch! It's an easy mod that requires only a single additional part--an on/on DPDT mini-toggle switch--and drilling a mounting hole for it in the enclosure. Directions and photos for the mod are available at viewtopic.php?p=476702#p476702

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I’m going to have to do that .


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Pedal building is like the opposite of sex. All the fun stuff happens before you get in the box.

Thanks! Planning to build it in the next couple of weeks. Will definitely do the mod.

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I don't want to ruffle any feathers, but although this mod does duplicate exactly the differences between the two versions of the Phase 90, and having the feedback resistor switched in does give you 'that sound', ... from an engineering point of view it is a bit of a bodge and always was. The intention of it seems to have been to introduce some resonance.

Without the feedback, as in the early version of the circuit, the Phase 90 produces two sharp swept filter notches. An ideal resonance mod would produce symmetrical peaks on either side and one in between those two notches. In addition to the phasing effect you get a touch of wah wah. The actual mod as introduce by MXR does make the sound more wah like, but at the expense of the notches, which are much reduced in depth and considerably broadened, so you loose a lot of the phasing effect. The pedal becomes much more like a swept wah wah. A plot of the resultant frequency response looks a bit of a mess.

The other thing that happens is that by introducing resonant peaks the signal level is increased at the peaks. The output circuit of the Phase 90 already tends to clip very easily, so with the resonance mod you get more distortion. There is a more elegant engineering solution to introducing resonance to the Phase 90 circuit, but that produces a Phase 90 that never existed.

My whole phaser building life has been a lie!


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Pedal building is like the opposite of sex. All the fun stuff happens before you get in the box.

Hahahahaaa!

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